Such measurement sensors are known, for example, from German published application DE-OS 24 15 583 and East Germany Patent DD-PS 127531.
More particularly DD-PS 127531, which most closely resembles the invention, discloses a vortex flowmeter comprising a damming member which is disposed in a flowed-through pipe and whose downstream side bears a plate whose surface is provided with strain gauges.
Vortex flowmeters are also known in which piezoelectric sensors of flowing media are disposed insulated inside or outside the damming member.
The operation of the vortex flowmeter is based on the fact that when medium flows on to the damming member, vortices are alternately induced on both sides of its end face and that the vortices form the so-called Karman vortex trail. As they become detached the vortices skim past the rear side of the damming member, where they induce alternating pressure loadings whose frequency depends on the flow velocity of the medium to be determined.
The prior art vortex flowmeters have the problem that it has proved impossible to obtain a construction resistant to temperature, temperature shock and corrosive media if use is made of strain gauges disposed on the outside of the plate. If piezoelectric sensors are disposed inside the damming body, they are mechanically so connected thereto that the entire measurement sensor has only limited resistance to temperature and temperature shock.